1. Field of the Invention
The present invention relates to a piezoelectric thin film device including a single or a plurality of film bulk acoustic resonators (FBAR).
2. Description of the Background Art
A film bulk acoustic resonator constituting a piezoelectric thin film device has hitherto been obtained by forming excitation electrodes, on both main surfaces of a piezoelectric thin film, opposed to each other with the piezoelectric thin film interposed therebetween, in an excitation region where vibrations are excited (e.g. see Japanese Patent Application Laid-Open No. 2003-318695).
However, there has been a problem with the conventional piezoelectric thin film device that a frequency impedance characteristic of the film bulk acoustic resonator is susceptible to spuriousness caused by vibrations in an unexpected mode.